1. Field of the Invention
The present invention relates to a manufacturing method for a composite substrate having an optical device wafer composed of a sapphire substrate and an optical device layer (epitaxial layer) formed on the front side of the sapphire substrate and a heat sink substrate bonded to the front side of the optical device layer in the optical device wafer.
2. Description of the Related Art
In an optical device fabrication process, an optical device layer of gallium nitride compound semiconductors is formed on the front side of a substantially disk-shaped sapphire substrate to form an optical device wafer, wherein the optical device layer is partitioned by a plurality of crossing streets to form a plurality of regions where optical devices such as light emitting diodes (LEDs) and laser diodes (LDs) are respectively formed. The optical device wafer is cut along the streets to divide the regions where the optical devices are formed from each other, thereby obtaining the individual optical devices (see Japanese Patent No. 2859478, for example). A heat sink member is bonded to an optical device for the purpose of heat radiation (see Japanese Patent Laid-open No. Sho 60-92686, for example).